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Plant structure and Function II - Coggle Diagram
Plant structure and Function II
Plant adaptations for extreme environments
Cacti
Leaves are reduced to a spike, low surface area for water loss by evapouration
Stomata are sunk in grooves to reduce transpiration
Swollen stem stores water
A shallow root system covers a large surface area to absorb rainfall
Spikes stop animals eating the plant to get water
Marram grass
Stomata are sunk into pits and fold within the leaf to trap moist air and reduce water loss
Thick waxy cuticle, which reduce water loss by evapouration
Curled leaves, reduce air flow close to the leaf, and reduces diffusion from the leaf into the air
Ridged inner surface for gas exchange
Conifer forest biome
Keep leaves during the winter
Leaves are reduced to needles, reducing the surface area for water loss
Thick waxy cuticle to decrease water loss
Water is mainly in forms of snow and ice
Deciduous forest biome
Very broad leaves, maximise light absorbtion
Shed their leaves during winter so less water is needed
Thin waxy cuticle
Thorns
Protect themselves from being eaten, by growing spikes
Acacia trees have large thorns home to colonies of stinging ants
Leaves can contain bad tasting chemicals
Plant hormones
Auxins
Plant hormone that controls growth
Respons to different stimuli and moves to the shaded side of root
Phototropism - plant growth in response to light
Gravitropism - plant growth in response to gravity
Produced in the rips of roots and shoots
Stimulates cell elongation process
Shoots
Towards light
When the shoot is exposed to light, more auxin accumulates on the shady side
This makes the cells elongate faster on the shaded side as there are more auxin
The shoot bends towards the light
Positively phototropic
Away from Gravity
When a shoot grows sideways, gravity produces an unequaly districution of auxin in the tip, more auxin on the lower side
The lower side grows faster as there are more auxin
The shoot bends upwards
Negatively gravitropic
Roots
Towards Gravity
More Auxin accumulates on the lower side
In a root, the extra auxin inhibits growth
The cells on top elongate faster
The root bends down
Positive gravitropism
Away from light
If a root starts being exposed to some light, more auxin accumulates in the shaded side
The auxin inhibits cell elongation
The root bends downwards
Negative phototropism
Roots deep undergound aren't exposed to light, they grow downwards due to positive gravitropism
Commercial use of Plant Hormones
Auxins
Selective weedkillers
Most Weeds are broad leafed
Spraying weeds with high concentrations of auxins upsets plant's growth pattern
This soon kills weeds as they can't keep up with the rapid growth
Narrow leave plants are fine
Rooting powder
A cutting is a part of a leaf which has been removed from a plant and doesnt have roots
If you add rooting powder, the plant will porduce roots
Allows you to produce clones
Gibberellins
Seed Germination
Allows famers to grow seeds at different times of the year
Some seeds need periods of cold or dark before germination
Can make plants flower earlier than they would naturally
Seedless fruit
Most plants only produce fruit after polination
This makes fruit contain seeds
Gibberellins can make fruits lik apples and grapes develop with fertilisation
No seeds in fruit
Ethene
Ripening hormone
Can be sprayed onto unripe fruits to make them ripen
Unripe fruit can be transported and then ripened at their destination to avoid bruising
Testing a leaf for starch
Take a plant which has been under bright ligtht
Fill a beaker with boiling water and place the leaf into it, to remove the waxy cuticle
Collect a boiling tube filled with ethanol and place the lead in it, this will remove the green colour (chlorophyll) from the leaf
After 10 minutes, rinse off the ethanol and lay out the leaf
Add iodine to the leaf, if it turns bluey black, starch is present
Starch is evidence for photosynthesis